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Author Topic: N-arylation and group (in)tolerance (Ullman)  (Read 1885 times)

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asa029

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N-arylation and group (in)tolerance (Ullman)
« on: May 23, 2011, 05:08:03 PM »

I wish to N-arylate a nitrogen-heterocycle (imidazole) by using Ullman-type conditions. This include bromomesityl, CuI and DMF with addition of base (here: K3PO4). My heterocycle also contain a carboxaldehyde function.

The article describing this procedure managed almost complete conversion (using unsubstituted heterocycle and less sterically hindered aryl). I was wondering if anyone had any previous experience with this sort of reaction, particularly the group (in)tolerance of the aldehyde function.
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Honclbrif

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Re: N-arylation and group (in)tolerance (Ullman)
« Reply #1 on: May 24, 2011, 01:24:11 AM »

Practically any time you combine an amine and an aldehyde, you've got to consider immine formation.
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asa029

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Re: N-arylation and group (in)tolerance (Ullman)
« Reply #2 on: May 24, 2011, 04:45:18 PM »

Practically any time you combine an amine and an aldehyde, you've got to consider immine formation.

Of course, but the amide-product is not found after the end of reaction (or during, for that matter). The only observed result is consumption of the carboxaldehyde, but nothing shows up on the GC, so I'm thinking complexation or degradation.
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bolo

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Re: N-arylation and group (in)tolerance (Ullman)
« Reply #3 on: May 31, 2011, 12:44:42 AM »

The reaction is also tolerant to -CO2H group, it also may take a role of an activating or 'easing' group. Look at the fenamic acid synthesis, though it's an example of Goldberg reaction, it's mechanism is quite similar.
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